Sun-mi declares her love for Oh-gong, wearing down his resolve and landing them in bed together. She tells him "I love you" over and over, saying she'll let out everything she'd built up inside.
Oh-gong says that he has something to say that she'll like, but doesn't tell her about removing the bracelet and instead says he'll show her later. Dude, you've only got two episodes left! Chop chop with the truth, monkey!
After hearing that Priestess is helping Buja's murderer, PK storms off to confront that murderer. Mawang hears about this from Dragon Prince Alice and is alarmed, because Mawang bound PK's powers after the last incident, and that puts PK in danger. Moreover, PK is also risking Oh-gong's whole master plan to defeat the dragon.
PK barges in on Kang Dae-sung, who is surprised at the random visit from a famous pop star. PK only gets as far as growling Buja's name (her human one) before he's stopped by Mawang, who places a forceful hand on PK's shoulder that keeps him subdued. PK fumes silently while Mawang "explains" that PK had been dating Buja, an idol trainee, and lost his reason when he heard she is now living with Kang Dae-sung.
Mawang asks what Kang's relationship to Buja is, and Kang lies that she's the daughter of a woman his foundation supports, assuring him that it's all aboveboard. Mawang apologizes for the trouble, and forcibly shoves PK out of the room.
As they leave, they run into Priestess in the corridor. PK starts after her menacingly, but Mawang restrains him firmly.
PK asks accusingly, "How could you do that?" Priestess looks conflicted, but just watches them leave with a sad expression on her face.
Back at the office, Mawang roars at PK for his foolishness, while PK yells at him to remove the tattoo binding his powers. Mawang says he promised not to interfere with Oh-gong's life-and-death mission, and orders the others to follow his lead. Priestess will die anyway when the black dragon dies, and Kang Dae-sung will fall as well, so PK will get what he wants.
Oh-gong wakes in bed to see Sun-mi sitting nearby, smiling at him. Over breakfast, she reminisces on some of her favorite moments with him, saying she'd like to do them again.
As she recounts their past dates, Oh-gong's mood grows sadder, particularly when she wonders whether she'll see the egret/doctor again, and what happened between her and the prior Sam-jang. Oh-gong suggests that she take Frosty and pay the doctor a visit to ask her questions, and Sun-mi agrees.
Sun-mi sighs about having to go to work, briefly considering playing hooky. But Oh-gong says he likes that she's the type who'd go on living no matter what happened, and she gets up to get ready.
Kang Dae-sung decides it's better to move Priestess out of his house—he hadn't considered how it looked to others to be living with a young woman. He asks Priestess if her host body was really dating PK, and she confirms that Buja had liked him.
Kang then asks if Sun-mi was really able to revive Buja's dead body, and Priestess sharply says they don't need her. But Kang is intrigued about Sun-mi's abilities, and says he'll have to meet her.
Mawang informs Oh-gong of PK's recent behavior, but adds that he won't involve himself in their business. He's back to his goal of attaining immortality, because once he's ascended to a powerful seat, he can look for his lost son. So he wants to steer clear of trouble.
Mawang asks how Oh-gong means to fight the black dragon, and Oh-gong replies that Frosty is making divine weapons, which includes a sword. He'll strike with that.
Those weapons (rock, bell, sword) were made using the energy of Kang Dae-sung's followers, and Frosty shows them to CEO Sa and Priestess. He prevents Priestess from touching them, saying he'll hand them over when needed.
Kang Dae-sung drops by Sun-mi's office, not fazed by her obvious mistrust of him. She calls him someone capable of destroying the world without caring about loss of lives, and rather than hearing this as "you're evil," Kang hears it as "you're powerful" and is pleased. Psycho villain is psycho.
Sun-mi warns him not to underestimate those he looks down on, because they have the power to drag him from power. She says she sees now why she, a human, is the one who must do this; her specialness was made from within that desire to be ordinary in an ordinary world. When she says she'll throw him out of her office, Kang grows angry and grabs her arms, yelling, "Don't look down on me!"
In that moment, Sun-mi has a vision, which Kang also glimpses: Within the river waters, the black dragon opens an eye. She's spooked by the vision, but it brings Kang hope and he thanks her for it.
Oh-gong decides that the plan will go into motion tonight. CEO Sa agrees to make the preparations, and Frosty is assigned to watch over Sun-mi.
Priestess is surprised to have the plans moved up but agrees, feeling confident that Kang Dae-sung will follow whatever orders she gives him.
Kang, meanwhile, has been invigorated by the vision, which gives him certainty that Priestess's promises were true and not just metaphors. When she confirms that the dragon's power will allow him to possess power greater than any king before him, his eyes go positively manic with glee.
Sun-mi, on the other hand, is perturbed and tries to figure out what her vision portends. She wonders if she will have to summon the dragon and if that will kill Oh-gong. But she recalls that the doctor lived, which is reassuring.
On her way out of the office, she has a vision of Han-joo in the future, sobbing on his daughter's wedding day. She tells him not to cry too much when his little girl gets married, and is happy at the thought that ordinary life continues on.
Frosty accompanies Sun-mi to visit the doctor, at Oh-gong's suggestion, and Oh-gong watches them leave from across the street. Earlier, he'd asked Frosty that in the event of his death, he should tell Sun-mi that Oh-gong had simply run away after the bracelet lost its hold on him.
Patriarch delivers a message from the heavens containing a deal for Mawang: If he finds the sword Oh-gong hid away, Mawang will be granted immortal status immediately. Mawang looks sorely tempted, but Secretary Ma firmly rejects the deal on his behalf, citing Mawang's integrity and loyalty, making it impossible for him to protest. Ha, Mawang looks so tortured to be forced to decline.
Even so, Mawang goes to the General Store to inquire about tools for finding the sword, like a metal detector. The shop owner's grandson comments that Patriarch was just here asking about a similar thing. Mawang asks the grandson to keep his visit a secret, then notices that the kid is back to calling him "Mawang-nim." The grandson admits that Grandma scolded him something fierce last time, saying that he wasn't supposed to call Mawang "ajusshi."
The grandson adds that PK was just here buying a lighter because he doesn't have the power to burn things himself. Mawang wonders if he should have removed the binding tattoo.
Priestess goes to PK's shoot and bewitches a staffer to deliver a message. That gets him to meet her, although he tries to leave the second he sees her, and she hastens to say that she's not helping Kang Dae-sung, but rather Oh-gong. PK says that's why he isn't killing her now—but he knows she's not Buja and is now able to go through with it.
Priestess is hurt, but insists that he won't kill her because Oh-gong is protecting her. PK sets her straight: "He isn't protecting you. He's risking his life to protect Sam-jang, so he's just tolerating you."
Priestess begs him to listen to her, and when she accidentally knocks him down, his lighter goes clattering to the ground. Realizing he's waiting to burn her up, she reminds him that he'd said earlier that he wouldn't. PK bites out that he'd been deceived then, and now intends to kill Priestess and burn the body for Buja's sake.
"Like this?" Priestess asks, and holds the flame to her arm, which smokes blue but then fades without damaging it. She says that her body won't burn while she's in it.
"Get out of that body, you crazy demon!" PK yells at her. Priestess screams, "I'm not a demon!" and throws the lighter down… and the flame lights at PK's feet and travels up his body, engulfing him in mystical fire. PK writhes in pain, and Priestess leaves him there.
She encounters Dragon Prince Alice in the hallway, and they trade barbs about her being a demon. Priestess snaps, "Everyone calls me a demon. Fine, I'm a demon. Demons should call demons." She stalks off, and Dragon Prince Alice hurries on to find PK caught up in smoky blue flames.
PK warns her to stay away, since Dragon Prince will catch fire too. He tells her to find Mawang, but Dragon Prince refuses to go, saying that although her powers are weak, she did come from a water kingdom. Thus, she'll put out the fire.
PK tries to push her away, but Dragon Prince Alice grabs him tightly. She says that she'll disappear once the flames are out, and tells him to think of it as her returning to her kingdom. PK struggles and yells for her to let go, but her grip is firm, and slowly the flames recede and her body goes limp. Water bubbles float up into the air, and PK sobs over her body.
Oh-gong and CEO Sa stand before the stone gate at the mouth of the dragon's river, where Oh-gong must defeat the dragon before it passes through. He hears that Sun-mi has arrived at the nearby village, and sighs that he's sorry to have sent her on a wild goose chase to see a doctor who isn't there anymore.
Sun-mi hears that the doctor moved away recently to go "very far away," and says to herself, "So it really was a lie." She explains to Frosty that she never believed Oh-gong's story that the doctor lived happily ever after with her Sam-jang. Sun-mi recalls the sadness in the doctor's face when they'd parted ways the last time, and decides to look around for possible clues.
Priestess arrives at a subway tunnel inhabited by homeless people, and as she walks among their midst, screams break out. By the time she arrives at the other end, she and the corridor are splattered with blood. Recalling Oh-gong's declaration to defeat the dragon before it emerged into the world, Priestess vows to draw it out.
Sun-mi is hit with another vision, this time of the doctor waiting in her office for something to arrive. She realizes that the doctor had called her and Oh-gong here, and left when she found whatever it is she'd been searching for. Since Sun-mi hadn't found anything, it must have been Oh-gong who did—but why did he keep it from her?
She heads off to ask him, but Frosty insists that she ask the doctor, suggesting that they look for her in the village. His insistence is rather suspicious, and Sun-mi guesses that they won't find her anywhere—and that Oh-gong meant to do something in her absence.
Frosty attempts to prevent her, but she asks if Summer Fairy had been happy when Frosty acted alone to protect her. She asks him to take her to Patriarch if he won't tell her what's going on, insistent that she know what's happening.
So Frosty takes her to Patriarch, and she requests that he tell her what has been kept from her.
Mawang hears what happened to PK and Dragon Prince, which spurs him to take action against Priestess, even if it messes with Oh-gong's plan. But Patriarch announces that the heavens will take care of Priestess, because Sun-mi has made the choice to fulfill her fate—and thus, the heavens will work to support her.
Mawang sighs, "So in the end, things will not happen as Sohn Oh-gong intends."
After Kang Dae-sung wraps up a class, he's confronted by student protestors picketing against him in the lobby. There are only three people but the sight troubles him, and he recalls Sun-mi's warning not to disregard the little people who could bring him down.
Priestess tells him to head for the river valley now, as preparations are complete. He notices blood near her face but isn't bothered by it, merely noting that she did something she needed to do. As he leaves, Priestess says to herself that Kang is well-suited to pair up with a demon.
Then she turns and freezes. Patriarch stands before her looking grim, with two heavenly assistants at his side, and Priestess gulps.
Oh-gong receives word of PK's injury and Dragon Prince's death. Mawang arrives at the valley and informs him that the heavens have stepped in to take care of Priestess, which interferes with Oh-gong's plan, since they need her to awaken the dragon.
Mawang asks why Oh-gong is overextending himself so much to fight the dragon, pointing out that if it's all for Sun-mi's sake, he could just tell her the truth and run away with her, dragon be damned. Oh-gong says lightly that doing so would ruin his image, because she thinks he's quite impressive. He adds, "I want to become even better. She makes me that way."
Mawang asks, "But don't you think she'll want to be impressive too, for you? And if she steps in to do that, could you stop her?" Oh-gong says that he can't stop her, which is why he's doing it this way. So Mawang sighs, "When it's over, come home, okay? I'll be bored."
Thanks to this latest wrench in works, Oh-gong decides to meet Patriarch to ask why he's interfering and demand Priestess's return. Patriarch says he's proud to see Oh-gong working to save the world and tells him he'll be reinstated in heaven when all is over.
At that, Oh-gong gets suspicious. Where is Priestess?
She's at the river gate, with Kang Dae-sung and the three heavenly artifacts. She touches the rock, which begins to shine, and the air ripples from the gate all the way to the dragon's sleeping place below the water.
Patriarch states that Priestess is calling the dragon, and Oh-gong realizes that this was a trap to keep him here. When Oh-gong tries to leave, he's encircled by a chain of men who send up a force field, trapping him inside.
Priestess cuts her palm with the sword, and the blood transforms into rose petals that fly toward the river. When they hit the water, the dragon's eyes open. She tells Kang Dae-sung that all that's left is for the dragon to come through the gate.
Oh-gong can feel when the dragon wakes, and sees from Patriarch's reaction that there's more to this. With dawning horror, he asks if Sun-mi is part of this.
As Priestess summons her energy to bring the dragon out, Sun-mi arrives and orders her to stop. Frosty shoves Priestess aside, and they both disappear amid wisps of smoke, leaving Sun-mi and Kang Dae-sung at the gate.
Oh-gong yells at Patriarch that he was going to take on this burden, but Patriarch thunders back that only Sam-jang can do this.
Seething, Oh-gong launches himself at his force field prison, but each attempt to breach it sends him flying back. "This is Sam-jang's will," Patriarch tells him. She was the one who asked that he be contained here.
Sun-mi picks up the sword and tells Kang that he can never become the master of that dragon—she will contain and destroy it. She starts to cut her palm with the blade, but Kang rushes at her. After a brief struggle, Kang ends up driving the sword through her abdomen, seemingly accidentally.
Staggering, Sun-mi coughs up blood, and a drop lands in the river. As the dragon starts to swim toward the gate, Kang reels back in horror and Sun-mi warns that he just chose his own destruction.
And then, the dragon makes its appearance, rising out of the river and into the sky. Sun-mi clutches her bleeding side and looks up as it starts to head straight for her…
Oh-gong summons all of his energy, and with a roar, he breaks through the barrier and vanishes from Patriarch's chamber.
Sun-mi falls to her knees before the gate, waiting for the dragon to finish the job… when suddenly Oh-gong appears and grabs the sword. As he wields it, white energy shoots from its tip up toward the dragon, creating a barrier at the gate. The dragon lurches toward it and is repelled, and starts to break up and crumble… and Oh-gong spits out a mouthful of blood, wounded by the effort.
As the dragon's form fades, the skies turn sunny and Oh-gong rushes to Sun-mi, who has collapsed on the ground. He cradles her body and vanishes with her.
Patriarch wonders how Oh-gong was able to defeat his barrier. Mawang arrives to inform him that he lent his energy to help Oh-gong see through his choice. But Patriarch warns that the black dragon has not completely disappeared, and the skies begin clouding over again.
Frosty and Priestess reappear in a distant field, and Priestess supposes the dragon will emerge soon. Frosty transports himself to the river gate, and as the dragon's scattered shape begins to reform, he uses his powers to freeze the gate shut.
Oh-gong takes Sun-mi to his garden, and her eyes flutter open when he calls her name. She tells him she's sorry, and sees from the state of the sky that things aren't over. She tells him he can't be here, but he refuses to go.
"You do everything I ask," she reminds him. "Go and finish things in my place. Truthfully, I'd wished your love wouldn't disappear, but now I'm fine. I feel better because of the bracelet."
Oh-gong cries wordlessly, and she adds, "When you are alone, it's a relief that the love won't remain." Then she falls limp.
Oh-gong cradles her body to his, sobbing, and lets out a roar of anguish.
Mawang feels Sun-mi's death within his own body. Patriarch says that nothing can stop the dragon now, but Mawang wonders what Oh-gong will do with this world in which Sun-mi is dead.
Frosty continues freezing over the gate while the dragon gains strength and the skies grow stormy, even as it takes a toll on his body. Oh-gong goes to where he'd hidden the sword he stole from Patriarch, and retrieves it.
The dragon finally blasts through Frosty's ice barrier, blowing Frosty backward violently and clearing the gateway. Oh no, is he dead too?
Oh-gong arrives with sword in hand, and charges to the gate to face down the dragon. Fire shoots from the blade, and he sends flames at the dragon, scoring a direct hit.
The dragon rears back before going back for another round, and Oh-gong's sword shoots up a fire shield this time. He struggles to hold his ground, when suddenly the golden bracelet and the sword both light up brightly.
Bolstered with additional energy, Oh-gong sends a fierce beam of light shooting at the dragon. The light pierces the dragon's entire body, which starts to break apart again.
Oh-gong falls to his knees, spent. The dragon bursts into ashes, and Oh-gong collapses on his back.
Light returns to the sky, and this time Patriarch declares the dragon gone for good.
"Sohn Oh-gong won," Mawang says.
Oh-gong looks up at the bright sky and says, "Jin Sun-mi, the world is the same, but you aren't here anymore." A tear falls from his eye, and then his eyes fall closed.